1. Field of the Invention
The present invention relates to the use of polymer mixtures containing, as essential components,
______________________________________ A) from 40 to 99% by weight of a polymer of an alkyl ester of (meth)acrylic acid, B) from 1 to 50% by weight of a copolymer of styrene and acrylonitrile having an acrylonitrile content of from 8 to 30% by weight, C) from 0 to 50% by weight of a rubber, and D) from 0 to 20% by weight of additives and processing auxiliaries, ______________________________________
for the production of moldings provided with an inscription with the aid of high-energy radiation.
2. Description of the Related Art
The production of laser-inscribed moldings from polymethyl methacrylate (PMMA) has hitherto been impossible in satisfactory quality without the addition of additives to increase the absorption coefficients of the laser radiation employed.
In particular for inscription with the Nd:YAG laser which is the most frequently used, pigments are added, but these adversely affect the transparency of the PMMA, which is frequently a prerequisite for the use of PMMA in the application. In the area of measuring beakers, scales and measuring rules, this is unacceptable; on the other hand, a durable inscription which is highly legible both in transmitted light and in incident light is desirable in these very applications.
The addition of carbon black to improve the laser inscribability of molding compositions comprising thermoplastics is described in DE-C 30 44 722, but this does not give satisfactory results in the case of PMMA.
Mixtures of PMMA and styrene-acrylonitrile copolymers (PSAN) are known and described, for example, in Polymer 28 (1987), 1177; at an acrylonitrile content of the PSAN in the range from 18 to 23% by weight, the transparency of moldings produced from the molding compositions is retained extremely well.